Various technologies for sorting and collecting solid particles and the like have been developed in both wet and dry type technologies in accordance with a wide range of objects to be sorted. Among these, a dry type sorting technology which uses not properties that depend on a material type, such as magnetism and electrification properties, but general versatile properties of a solid, such as specific gravity and particle diameter, for example, a technology which applies an inertial force and a wind force has been proposed. Many of these sorting methods are configured to function by combining a centrifugal force or an inertial force, a drag force (gas resistance or the like), transportation effect by an airflow, and a falling motion caused due to gravity, and separate light weight objects and heavy object, has been developed as a technology.
What is required for industrial use as a sorting machine is high versatility. In other words, the ability to simply, easily, and widely adjust the sorting ability to be capable of sorting various types of objects to be sorted which exhibit various physical properties is required. In addition, achieving high sorting accuracy, and being realizable by initial investment and operating costs that correspond to the object is also required. In particular, in the recycling field, such as urban mines where demand has been rapidly increasing in recent years, more cost-effective sorting technology than that of the related art, is required.
In an airflow sorting machine which uses a vertical column as a sorting tank, a dedicated area is narrow and relatively high sorting efficiency can be obtained (for example, refer to Patent Documents 1 to 8). In order to achieve high sorting accuracy with the airflow sorting machine, a certain column length is required, and particularly in a case of a multistage configuration for simultaneous sorting of many types at the same time, a space in the height direction becomes more necessary and becomes a constraint to the installation location (for example, refer to Patent Documents 1 to 7).
Similarly, as a sorting device which uses a vertical column, a sorting device which is provided with a suction port between an input port for inputting an object to be separated into a column and an air supply port for supplying an airflow into the column, and which suctions the object to be separated from the suction port together with the airflow, is known. Since the sorting is performed at a suction port part of the column with respect to the airflow sorting device of the related art which performs the sorting using substantially the entire column, the occupied space in the height direction can be reduced (for example, refer to Patent Document 8). Meanwhile, a difference in gravity falling velocity for each object to be separated can adversely affect the sorting accuracy, and a braking mechanism for mitigating such a difference is required to improve the sorting accuracy (for example, refer to Patent Document 8).